The invention relates to a method for automatically detecting the sensitivity of sensors, in particular of piezoelectric sensors with individual sensitivities, sensors with a sensitivity around a specific value being assigned to a sensor group.
Sensors are currently being used in many technical fields for the purpose of detecting states, positions etc. The method described below relates chiefly to sensors that are differentiated by an individual sensitivity. It is merely preferred for the method to relate to piezoelectric sensors with the aid of which pressure, force or acceleration can be determined.
Such sensors are used, for example, in injection molds in order to determine a cavity pressure. The cavity pressure can then be used to determine, for example, the degree of filling of a cavity or the instant for the switchover from filling pressure to follow-up pressure.
A serious problem in handling such sensors resides in the individual sensor sensitivities, which are given in pC/bar (picocoulomb/bar) for pressure, or pC/N (picocouloumb/newton) for force. This sensitivity differs for each sensor for production reasons.
U.S. Pat. No. 4,695,955 discloses an electronic device that offers a universal interface between sensors and a processing system for the signals emanating from the sensors. In this case, the identification element for automatically detecting the sensor are shown. These identification elements comprise resistors.
U.S. Pat. No. 3,943,440 concerns a method of the above-named type, but not in relation to piezoelectric sensors. Instead, it describes elements for setting the sensitivity of a measuring circuit, a coding resistor being connected to the measuring circuit by a single wire. A current is conducted through this resistor via the wire. The voltage of the resistor is measured and coded in binary form by means of an A/D converter, in order to set the sensitivity of the measuring circuit.